Gas generation



H. F. SMITH.

GAS GENERATION.

APPLICATION FILED NOV. 20. 1918.

Patented Oct. 18, 1921.

UNITED STATES PATENT-'- OFFICE.

HARRY F. SMITH, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE GAS RESEARCH OOMPA N Y, OF DAYTON, OHIO, A CORPORATION OF OHIO.

GAS GENERATION.

Specification of Letters Patent.

Patented Oct. 18, 1921.

Application filed November 20, 1918. Serial Nd. 268,407. 7

To all whom it may concern.

Be it known that I, HARRY F. SMITH, a citizen of the United States of America, residing at Dayton, county of Montgomery, State of Ohio, have invented. certain new and useful Improvements in Gas Generation, of which the following is a full, clear, and exact description.

This invention relates to a method of producing gas from carbonaceous fuel, and more particularly to an improved method of generating gas whereby the character of the hydrocarbons contained therein is controlled to roduce a gas of more desirable nature and? at the same time a resulting tar which is in a condition permitting greater ease in its handling.

One object of the invention is to so govern conditions during generation of the gas that the character of the hydrocarbons contained in such gas may be controlled as desired.

Another object is to so govern conditions within the generating chamber that the tar resulting from the condensation of the heavier hydrocarbons given off during the reaction will be of such a fluent character that it lends itself to easier handling.

Another object of the invention is to generate a gas, from carbonaceous fuel, which is of comparatively high heat value.

Still another ob]ect is to provide apparatus for carrying out this method of gas generation.

Other and further objects and advantages will be apparent from the following description, when taken in connection with the drawing herewith.

I have shown the apparatus for carrying out my method as applied to a well known suction, up-draft, gas producer. My invention, however, is not so limited in its applicability but is capable of general application, it being shown in connection with a gas producer merely for purposes of easier and clearer description.

In the drawing, in which like characters of reference designate like parts throughout the several views thereof,

Figure 1 is a view, partly in section and partly in elevation, of a gas producing apparatus adapted for carrying out my method of gas generation; and

Fig. 2 is a top plan view of the generator illustrated in Fig. 1, showing the arrangement of the tar return pipes and nozzles.

In the drawing, 10 designates the metallic shell of a conventional producer, such producer having a fire brick lining 11, a metal- 110 top 12, a grate 13, an air and moisture inlet 14, a gas olftake 15 and a fuel supply mechanism 16. Carried upon the grate 13, when in operation, is a fuel bed 17, of coal or other carbonaceous material. This fuel bed is divided generally into three zones A, B and C.

The producer illustrated is a conventional up-draft suction producer the air and moisture, usually steam, being introduced through the inlet 14 and led upwardly through the fuel bed where the chemical reactions take place resulting in the generation of the gas which passes off through the ofl'take opening 15. In such a producer the lower zone A of the fuel bed represents a zone of complete combustion, the carbonaceous material being oxidized in the presence of the air to form carbon dioxid, some'of the moisture in the incoming mixture of air and moisture being decomposed upon contact with the incandescent carbonaceous material to form hydrogen and oxygen, which oxygen will unite with the carbon to form more carbon dioxid. The intermediate zone B is a reducing zone in which the carbon dioxid resulting from the reaction in the zone A is reduced in the presence of incandescent carbon to carbon monoxid. The zone C is the so-called distillation zone. This zone contains the fresh or green fuel added to the fire to maintain the fuel bed continuously of the desired thickness and consistency. The fuel forming this zone C is raised to a sufficiently high temperature to drive off therefrom the volatile hydrocarbons contained in the fuel.

The volatile hydrocarbons driven olf from the fuel in the zone C probably comprise compounds ranging all the way from the simple methane to the complex and extremely heavy hydrocarbons, such as pitch. The hydrocarbons, such as methane, which are gaseous at ordinary temperatures, will mix with the hydrogen and carbon monoxid resulting from the reactions within the zones A and B and will pass off with such mixture as fixed gases. The heavier hydrocarbons,

temperatures, and which are generally known as tar, will condense as soon as the temperature is lowered sufficiently and thus cause considerable trouble, as by gumming up the valves to gas engines, etc.

In order to prevent the troubles arising from the presence of the heavier hydrocarbons these hydrocarbons are removed. In the type of producer illustrated the gas passing off through the offtake 15 passes downwardly through the downcomer 20, which opens into the bottom of the con denser or cooler 21, The condenser 21 has bafile plates 22 arranged therein upon which water is sprayed, which, as it trickles downwardly over the baffle plates, comes into intimate contact with the upwardly moving gas and thus tends to cool and wash The upwardly moving gas passes out of the condenser through the'pipe 23 which leads to an exhauster-pump 24:. This exhauster is adapted to draw the gas from the generating chamber and force that gas through the remainder of the system. The

cooled gas passing from the exhauster is forced through the extractor 25. This extractor may be of any desired type, but the type illustrated is that disclosed in my Patent No. 1,099,773 issued June 9, 1914. De-

tails of the structure of this type of tarextractor are therefore, not shown or described. As described in the patent above referred to, the gas as it passes through the extractor has the minute drops of the tar vapor or fog therein agglomerated into large drops which separate out under the action of gravity as the velocity of the gas is slowed down in the separator 26. This separator consists, substantially,.of an enlargement in the gas main with a baffle 27 extending transversely thereacross, the enlargement and baffle together serving to slow down the velocity of the gas considerably. As the velocity of the gas is slowed down the tar carried therein will separate out and collect in the sump or tank 28, the purified gas passing on through the main 29 which leads the gas to any desired place of use.

The tar ordinarily present in producer, or other analogous gas is very heavy and viscous and an extremely difficult material to handle. And one of the most serious difficulties heretofore encountered in producer gas operation has been the disposal of this tar.

As set out above, one of the objects of the invention is to so govern conditions during generation of the gas that the character of the hydrocarbons evolved may be controlled.

I have found that if the heavy hydrocarbons or tar removed from the gas are returned to the generating chamber and sprayed therein in such wise that it is distributed uniformly over the upper surface of the zone C of the fuel bed the resulting gas will have a considerably higher heat value than is the case where such tar is not returned to the generating chamber. It is admittedly old to introduce heavy hydrocarbons of various kinds into the generating chamber of a producer. One method of introducing into the generating chamber the heavy hydrocarbons removed from the gas is disclosed in my Patent No. 928,809 patented July 20, 1909. My present method, however, differs from those heretofore known and practised in that the tar is returned to the generating chamber and introduced onto the fuel bed in such wise as to be present in a vaporized form within the distilling zone. In other words in my patent just referred to the heavy hydrocarbons removed from the gas are introduced-into the fuel bed and are passed into the zones A and B. 'In this invention, however, the heavy hydrocarbons are introduced into the generating chamber and directly onto the fuel constituting the zone C. Consequently these hydrocarbons are vaporized at the same time that the volatile matter in the fuel is distilled therefrom.

I have found that where the heavy hydrocarbons are thus introduced into the generating chamber and upon the fuel bed, to substantially twice the quantity normally produced therein, the BTU value of the gas generated from a particular coal will frequently average from 20 to 30 BTU higher than is the case where the heavy hydrocarbons are notihus returned, this increase being sometimes as much as 60 BTU. To 'be specific a coal which gives a gas having an average of 170 BTU without the introduction of the heavy" hydrocarbons will frequently give a as having an average of from 190 to 200 BTU when such hydrocarbons are introduced and will sometimes average as high as 230 BTU. Of course the quantity of tar returned need not be in this particular proportion. And in ordinary practice the tar will generally be re turned at substantially the rate at which it is separated from the gas, all the tar being thus satisfactorily disposed of. For thus returning the hydrocarbons to the fuel bed I make use of the apparatus illustrated in the drawing, although it is to be understood that other forms of apparatus might be equally satisfactory for carrying this particular method into effect. the tar sump 28 has leading off from the bottom thereof a pipe 30 which constitutes the inlet pipe to the pump 31. Leading off from the pump 31 is a pipe 32 which opens into a manifold 33 running across the top of the producer. Leading off from this manifold are a plurality of pipes 34, there being shown in the drawing four of these pipes, the free ends of these pipes being closed in any desired manner. These pipes As illustrated I the top of the producer. Opening off from each of these pipes 34 and extending through the top of the producer, with their open ends terminating within the interior of the enerating chamber and above the top sur ace of the fuel bed, are a series of nozzles 35 through which any tar pumped from the sump 28 through the pipe 32, manifold 33 and pipes 34 will pass and be introduced into the generating chamber and upon the fuel in the zone C of the fuel bed. Aswill be noted by reference to Fig. 2 of the drawing these nozzles 35 are so arranged that the tar or hydrocarbons passing therefrom will be evenly distributed throughout the generatin chamber and over the fuel constituting t e zone C. Arrangement of the nozzles to secure such distribution of the tar seems essential if the desired results are to be obtained, and unles the tar is sufficiently distributed it will tend to quench the fuel bed, in spots, and will work completely through the fuel bed into the ash pit, thus seriously interfering with eflicient and satisfactory operation of the producer. The tar need not be introduced in the form of a finely divided spray, but should be so divided, or sprayed, and distributed that there will beno undue cooling or quenching of any part of the fuel bed.

In operating a producer such as disclosed a mixture of air and moisture, usually in the form of steam, is passed'through the fuel. bed in the conventional manner, as shown, an exhauster or pump being provided for sucking this mixture into the gencrating chamber and through the fuel bed. The hot gases generated from the reaction in the zones A and B pass upwardly through the layer of comparatively cool fuel C where the heat from such gases will raise the temperature of this fuel sufliciently high to cause the distillation of volatile hydrocarbons contained therein. The gas, with these hydrocarbons therein, passes through the condenser and tar extractor where the tar is removed therefrom, such tar being then pumped into the pipes 34: whence it is introduced into the generating chamber through the nozzles 35. It is not necessary that these nozzles be of any special design,-

ordinary small bore pipes without any special form of nozzle being entirely adequate. The tar, which consists of heavy hydrocarbons, is sprayed evenly over the fuel bed where it will be vaporized at the same time, and in immediate contact with, the gases evolved during the distillation process. As a result the hydrocarbons resulting from the distillation will contain a considerably larger proportion of lighter hydrocarbons, the result being a gas richer in hydrocarbons such as methane and therefore of higher heat value, and a tar also richer in lighter hydrocarbons and, therefore, one which is comparatively much more fluent and easy to handle.

In the method of gas generation described herein it is the desire to produce a gas especially rich in lighter hydrocarbons, such as methane, and a1 tar also rich in comparatively lighter hydrocarbons. Consequently the driving off of hydrocarbons from the fuel is accomplished in an atmosphere saturated with heavy hydrocarbons. If it were desirable to get a gas, or tar, of a different character the atmosphere in which such distillation is accomplished would be varied accordingly. While the enriching of the gas is an especially important advantage attendant upon the practising of the invention, the returning of the tar to the enerating chamber in such Wise as to keep own the quantity of tar which is at any one time present in the tar handling apparatus and to give a more fluent tar, which permits of greater ease in handling, are also especially important advantages.

As stated above this invention is by no means limited in its applicability to the generation of producer gas and its operation is not limited to the use of such apparatus as disclosed but is capable of being applied generally where the generation of gas from carbonaceous material comprises the distillation of volatile hydrocarbons. For example, where this method is applied in the generation of producer gas it is practicable to eliminate the spray nozzles for introducing the tar onto the fuel in the distilling zone and to, in place thereof, introduce fuel already covered with tar or heavy hydrocarbons. Also this invention is applicable to the generation of other than producer gas, as for instance bench gas.

While the method herein described, and the form of apparatus for carrying this method into effect, constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What I claim is:

1. The method of generating gas from solid carbonaceous fuels which consists in subjecting the lower zones of the fuel bed to partial combustion, passing the resulting hot gases through the upper zone of the fuel bed to drive off the volatile hydrocarbons therein, removing the heavy hydrocarbons from the offcoming gas; and returning such heavy hydrocarbons to the generating chamber in such wise as to distribute them evenly over the fuel bed.

2. The method of generating gas from solid carbonaceous fuels which consists in subjecting the lower zones of the fuel bed to: partial combustion, passing the resulting hot gases through thejupper zone of the fuel bed to drive off the volatile hydrocarbons therein, removing the heavy hydrocarbons from the offgoinggas; and spraying such heavy hydrocarbons over the entire fuel bed.

3. The method of generating gas which consists in maintaining a fuel bed of solid carbonaceous material Within the generating chamber of a gas producer, subjecting the lower zones of the fuel bed to partial combustion, passing the hot gases through the upper zone of the fuel bed to drive off from such fuel the volatile hydrocarbons therein, removing the heavy hydrocarbons from the offgoing gases; and returning such hydrocarbons to the generating chamber and above I the fuel bed.

4. The method of increasing the BTU value of producer gas which consists in removing the heavy solid hydrocarbons from the gas and returning them to the generating chamber of the producer in such wise as to distribute them evenly over the fuel means for returning such heavy hydrocar bons to the generating chamber in such wise as to distribute them evenly over the entire fuel bed.

7. A gas producer comprising a generatingv chamber adapted to contain a fuel bed, means for removing the heavy hydrocarbons from the gas evolved; and means for returning such heavy hydrocarbons to the generating chamber, such means comprising nozzles arranged to distribute the returned hydrocarbons evenly over the fuel bed.

8. The method, in the operation of gas producers, which consists in removing the tar from the generated gas; returning such removed tar to the generating chamber; and distributing it therein in such wise that substantially all-the volatile constituents of the tar are driven off within the zone in which hydrocarbons are being evolved from the fuel bed.

9- In the generation of producer gas, which gas when withdrawn from the generating chamber contains a substantial quantity of normally liquid hydrocarbons or tar, the method of disposing of said tar which. consists in separating it from the gas, collecting such separated tar, returning it to the generating chamber of the producer, and distributing it over the fuel bed therein, the tar being returned to the generating chamber at substantially the rate at which it is separated from the gas.

10. In gas generating apparatus comprising a generating chamber adapted to contain a fuel bed of carbonaceous material, means for blasting said fuel bed with air and steam to generate gas, which gas contains a substantial quantity of normally liquid hydrocarbons or tar; a separator for removing from the generated gas such tar, a sump in which such separated tar is collected; and means for returning the tar to the generating chamber, constructed to return the tar at substantially the rate at which it is separated from the gas and to distribute it over the surface of the fuel bed.

11. In the generation of producer gas, in which a fuel bed of solid carbonaceous material is maintained within the generating chamber of the producer, the lower zone of the fuel bed being subjected to partial combustion, and the resulting hot gases passed through the upper zone of said fuel bed to drive off the volatile hydrocarbons or tar therefrom; the method of disposing of such tar, which consists in separating it from the gas, returning said separated tar to the generating chamber of the producer, and distributing it over the fuel bed therein, the quantity of tar returned to the generating chamber being not less than twice the quantity normally produced when tar return is not practised.

In testimony whereof I affix my signature.

HARRY F. SMITH.

Witnesses:

J. W. MCDONALD, M. A. PEASE. 

